Nitride with low lattice oxygen content and preparation method thereof

Abstract

The invention provides a nitride with low lattice oxygen content and a preparation method thereof, and relates to the technical field of ceramic materials. The preparation method comprises the following steps: mixing an oxide raw material and a carbon source to obtain a precursor, the oxide raw material being Al2O3 powder or SiO2 powder; placing the precursor in a reaction furnace, raising the temperature to 700-900 DEG C, and introducing N2 and halogen gas for activation to obtain an activated product; the temperature is increased to 1300-1600 DEG C, the gas atmosphere is kept unchanged, the activated product is subjected to carbon thermal reduction, and a reduction product is obtained; and keeping the temperature of the reaction furnace unchanged, introducing a passivating agent, and generating a sealing layer on the surface of the reduction product. According to the method, halogen gas is introduced to cooperate with bulk carbon thermal reduction and halogen free radical deep penetration, so that the problem of bulk phase oxygen removal is solved, the lattice oxygen content of a product is remarkably reduced, the thermal conductivity and insulativity of the material are improved, and the method can be suitable for the fields of electronic packaging, optical materials, high-performance ceramics and the like with high oxygen content control precision requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic materials, and particularly relates to a nitride with low lattice oxygen content and a preparation method thereof. BACKGROUND

[0002] Aluminum nitride and silicon nitride are widely used in the fields of electronics, optics, ceramics, thermal conductive materials, etc. Especially in electronic packaging materials, aluminum nitride has a wide application prospect due to its excellent thermal conductivity, mechanical strength and electrical insulation. However, in the existing preparation technology, carbon thermal reduction method is mainly used to prepare nitride powder with small particle size and good dispersity. However, during the reaction process, part of the oxygen will replace the position of nitrogen to form lattice oxygen, and aluminum vacancies will be generated to balance the valence state, thereby forming point defects in the nitride. These lattice oxygens will affect the physical properties such as electrical conductivity and thermal conductivity, and reduce the performance of the material. In order to reduce the content of lattice oxygen, the existing preparation method adopts direct nitriding method to directly react nitrogen gas with aluminum or silicon powder, and the source of oxygen is usually from impurities in raw materials or oxidation phenomenon in the reaction process. The reaction process needs to be broken and reacted continuously, which is complex and high in cost, and the particle size of the powder is uneven. In addition, some existing technologies improve the reaction atmosphere or use raw materials with higher purity, but there is still a problem of high oxygen content.

[0003] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present application, and therefore can include information which does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a nitride with low lattice oxygen content and a preparation method thereof.

[0005] According to a first aspect of the present application, a preparation method of a nitride with low lattice oxygen content is provided, comprising: S1, mixing an oxide raw material and a carbon source to obtain a precursor, the oxide raw material being Al2O3 powder or SiO2 powder; S2, placing the precursor in a reaction furnace, heating to 700-900℃, and introducing a first mixed gas containing N2 and halogen gas to activate to obtain an activated product; S3, heating to 1300-1600℃, keeping the gas atmosphere unchanged, and making the activated product perform carbon thermal reduction to obtain a reduced product; S4, keeping the temperature of the reaction furnace unchanged, introducing a passivation agent, and generating a sealing layer on the surface of the reduced product to obtain a nitride with low lattice oxygen content.

[0006] In one of the embodiments of the present application, in step S2, the halogen gas is selected from Cl2 and / or CCl4, and the volume fraction of the halogen gas in the first mixed gas is 10-20%.

[0007] In one of the embodiments of the present application, in step S2, the activation time is 1-3h.

[0008] In one of the embodiments of the present application, in step S3, the furnace cavity of the reaction furnace is controlled to be in a micro-negative pressure state of-0.02--0.04MPa.

[0009] In one of the embodiments of the present application, in step S4, when the oxide raw material is Al2O3, the passivation agent is SiCl4, so as to generate a Si3N4 sealing layer on the surface of the reduction product.

[0010] In one of the embodiments of the present application, in step S4, when the oxide raw material is SiO2, the passivation agent is AlCl3, so as to generate an AlN sealing layer on the surface of the reduction product.

[0011] In one of the embodiments of the present application, in step S3, the time of the carbothermic reduction reaction is 3-4h.

[0012] In one of the embodiments of the present application, in step S1, the molar ratio of the carbon source to the oxide raw material is 98%-102% of the stoichiometric ratio.

[0013] In one of the embodiments of the present application, in step S4, after the passivation agent is introduced for 8-15min, argon quenching is performed.

[0014] In a second aspect of the present application, a nitride with low lattice oxygen content is provided, which is prepared according to the preparation method of any one of the above.

[0015] The nitride with low lattice oxygen content and the preparation method thereof provided in the embodiments of the present application have the following beneficial effects: The preparation method of the nitride with low lattice oxygen content provided in the embodiments of the present application can effectively remove impurities in the reaction process by adopting the carbothermic reduction method and supplementing halogen atmosphere control and post-processing measures, so as to obtain aluminum nitride or silicon nitride with higher purity, the lattice oxygen content of the aluminum nitride or silicon nitride is ≤0.1 wt%, so as to improve the thermal conductivity and electrical conductivity of the material, and the method is widely applicable in the fields of high-end electronic materials, ceramic materials, etc.

[0016] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present disclosure, and therefore should not be considered as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor under the premise of the drawings.

[0018] Figure 1 SEM image of AlN prepared in Example 1 of the present disclosure.

[0019] Figure 2 SEM image of Si3N4 prepared in Example 2 of the present disclosure. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely. If the specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased in the market.

[0021] The embodiments of the present disclosure provide a preparation method of nitride with low lattice oxygen content, comprising: Step S1, mixing an oxide raw material and a carbon source to obtain a precursor, wherein the oxide raw material is Al2O3 powder or SiO2 powder; Step S2, placing the precursor in a reaction furnace, heating to 700-900°C, and introducing a first mixed gas containing N2 and halogen gas to activate to obtain an activated product; Step S3, heating to 1300-1600°C, keeping the gas atmosphere unchanged, and making the activated product perform carbothermic reduction to obtain a reduced product; Step S4, keeping the temperature of the reaction furnace unchanged, introducing a passivation agent, and generating a sealing layer on the surface of the reduced product to obtain nitride with low lattice oxygen content.

[0022] Specifically, in one of the embodiments, in step S1, the molar ratio of the carbon source to the oxide raw material is 98%-102% of the stoichiometric ratio. For example, when AlN is prepared by carbothermic reduction method, the stoichiometric ratio of C and Al2O3 is 3:1. In the traditional preparation process, excess C (about 20%) needs to be added, for example, the molar ratio of C to Al2O3 is 3.6:1, to ensure the carbothermic reduction reaction. In the present embodiment, by using halogen atmosphere and gradient reduction process, the molar ratio of C to Al2O3 is 3:1, which can avoid the addition of excess carbon for reaction and the residual carbon.

[0023] Specifically, in step S1, the carbon source can be selected from glucose, petroleum coke, carbon nanotubes, etc., and this disclosure does not impose specific restrictions.

[0024] Specifically, in one embodiment, in step S2, the halogen gas is selected from Cl2 and / or CCl4, and the volume fraction of the halogen gas in the first mixed gas is 10-20%, for example, 12%, 15%, 18%, etc. Further, in this step, the activation time is 1-3 hours. In this step, the temperature is relatively low (700-900℃) for low-temperature halogen activation, which activates lattice oxygen and generates MOCl. x This achieves gas-phase removal. Among them, MOCl... x In the text, M represents an element in the oxide raw material, such as Al or Si.

[0025] Specifically, in one embodiment, the carbothermic reduction reaction time in step S3 is 3-4 hours. Further, in this step, the furnace cavity of the reactor is controlled under a slight negative pressure of -0.02 to -0.04 MPa. This step involves the reduction reaction, and through the synergistic introduction of halogen gas, halogen free radicals deeply penetrate the furnace. Under the attack of halogen free radicals (e.g., Cl· free radicals), the MO bonds break (M is Al or Si), resulting in bulk deoxidation and solving the problem of difficult removal of bulk oxygen. Furthermore, by controlling the reactor to be under slight negative pressure, the removal of gaseous products can be promoted, further improving the purity of the product. Through steps S2 and S3, under the action of the gradient temperature field, oxygen diffusion channels are opened, and in conjunction with the halogen atmosphere, the lattice oxygen content of the product is greatly reduced.

[0026] Specifically, in one embodiment, when preparing AlN, the oxide raw material is Al2O3, and in step S4, the passivating agent is SiCl4 to form a Si3N4 sealing layer on the surface of the reduced product (AlN). Correspondingly, when preparing Si3N4, the oxide raw material is SiO2, and in step S4, the passivating agent is AlCl3 to form an AlN sealing layer on the surface of the reduced product (Si3N4). In this step, a sealing layer is formed on the powder surface through high-temperature passivation, thereby sealing the oxygen channels and blocking oxygen back-permeation that occurs during the cooling process.

[0027] Furthermore, in one embodiment, in step S4, after introducing the passivating agent for 8-15 minutes, argon quenching is performed. The argon flow rate is 20-50 L / min, and the temperature is room temperature (20-35°C). Argon quenching can rapidly reduce the material temperature, thereby "freezing" the low-oxygen lattice state and avoiding secondary oxidation or oxygen adsorption in the medium-low temperature range. This helps to obtain nitride products with extremely low lattice oxygen content and stable performance.

[0028] This invention also provides a nitride with low lattice oxygen content, prepared according to the above-described preparation method. The nitride prepared by this method can achieve a lattice oxygen content of less than 0.1 wt%. Furthermore, it eliminates the need for adding excessive carbon source, avoids post-treatment steps such as acid washing, and prevents secondary contamination.

[0029] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0030] Example 1 This embodiment provides an AlN with low lattice oxygen content, obtained by following the steps below: (1) Prepare high-purity Al2O3 powder (D50=0.8 μm, oxygen content about 0.6 wt%) and glucose. Mix the high-purity Al2O3 powder and glucose according to the molar ratio of C to Al2O3 of 3:1 to obtain a mixture.

[0031] (2) Place the mixture obtained in step (1) in a negative pressure resistant reactor, heat it to 850°C, introduce N2 and Cl2 with a volume ratio of 85:15, react for 1.5 h to obtain reactant I.

[0032] (3) Keep the reactor under a slight negative pressure of -0.03MPa, keep the gas atmosphere constant, raise the temperature to 1500℃, keep it at the temperature for 4h, and obtain reactant II.

[0033] (4) Keep the reaction temperature constant, introduce SiCl4, maintain for 10 min, and then quench with argon gas (flow rate 40 L / min, room temperature) to obtain AlN with low lattice oxygen content.

[0034] The AlN powder obtained in this embodiment was measured to have a lattice oxygen content of 0.07 wt%, a total oxygen content of 0.12 wt%, and a specific surface area (BET) of 8.8 m². 2 / g.

[0035] The method for determining lattice oxygen is: pulse heating inert gas melting-infrared absorption method. For specific operation methods, please refer to the content of patent ZL 202111304794.7 "A method for determining the lattice oxygen content of aluminum nitride".

[0036] The method for determining the total oxygen content is: pulse heating inert gas melting-infrared absorption method, see standard GB / T 16555-2017 "Chemical Analysis Methods for Carbon-containing, Silicon Carbide and Nitride Refractory Materials".

[0037] Example 2 This embodiment provides a Si3N4 with low lattice oxygen content, obtained by following these steps: (1) Prepare high-purity SiO2 (D50=0.8 μm, oxygen content about 0.6 wt%) and glucose. Mix the high-purity SiO2 powder and glucose according to the molar ratio of C to SiO2 of 2:1 to obtain a mixture.

[0038] (2) Place the mixture obtained in step (1) in a negative pressure resistant reactor, heat it to 750°C, introduce N2 and Cl2 with a volume ratio of 80:20, react for 2 hours to obtain reactant I.

[0039] (3) Keep the reactor under a slight negative pressure of -0.03MPa, keep the gas atmosphere constant, raise the temperature to 1350℃, keep it at the temperature for 5h, and obtain reactant II.

[0040] (4) Keep the reaction temperature constant, introduce AlCl3, maintain for 10 min, and then quench with argon gas (flow rate 40 L / min, room temperature) to obtain Si3N4 with low lattice oxygen content.

[0041] The Si3N4 powder obtained in this embodiment was measured to have a lattice oxygen content of 0.08 wt%, a total oxygen content of 0.13 wt%, and a specific surface area (BET) of 10.1 m². 2 / g, wherein the methods for determining lattice oxygen and total oxygen content are as described in Example 1.

[0042] Example 3 This embodiment provides an AlN with low lattice oxygen content, obtained by following the steps below: (1) Prepare high-purity Al2O3 powder (D50=0.8 μm, oxygen content about 0.6 wt%) and glucose. Mix the high-purity Al2O3 powder and glucose according to the molar ratio of C to Al2O3 of 3:1 to obtain a mixture.

[0043] (2) Place the mixture obtained in step (1) in a reactor, heat it to 850°C, introduce N2 and Cl2 with a volume ratio of 85:15, react for 1.5 h to obtain reactant I.

[0044] (3) Keep the gas atmosphere in the reactor constant, raise the temperature to 1500℃, and keep it at that temperature for 4 hours to obtain reactant II.

[0045] (4) Keep the reaction temperature constant, introduce SiCl4, maintain for 10 min, and then quench with argon to obtain AlN with low lattice oxygen content.

[0046] The AlN powder obtained in this embodiment was determined to have a lattice oxygen content of 0.11 wt%, a total oxygen content of 0.24 wt%, and a specific surface area (BET) of 8.1 m². 2 / g, wherein the methods for determining lattice oxygen and total oxygen content are as described in Example 1.

[0047] Comparative Example 1 This comparative example provides an AlN, which is obtained by following these steps: (1) Prepare high-purity Al2O3 powder (D50=0.8 μm, oxygen content about 0.6 wt%) and glucose. Mix the high-purity Al2O3 powder and glucose according to the molar ratio of C to Al2O3 of 3.6:1 to obtain a mixture.

[0048] (2) Place the mixture obtained in step (1) in a reactor, heat it to 850°C, introduce N2, and react for 1.5 h to obtain reactant I.

[0049] (3) Keep the gas atmosphere in the reactor constant, raise the temperature to 1500℃, and keep it at that temperature for 4 hours to obtain reactant II.

[0050] (4) Heat-treat reactant II at 700℃ for 4 hours to remove carbon and remove excess carbon source.

[0051] The AlN powder obtained in this comparative example was found to have a lattice oxygen content of 0.26 wt%, a total oxygen content of 0.85 wt%, and a specific surface area (BET) of 8.1 m². 2 / g, wherein the methods for determining lattice oxygen and total oxygen content are as described in Example 1.

[0052] Comparative Example 2 This comparative example provides a Si3N4 with low lattice oxygen content, obtained according to the following steps: (1) Prepare high-purity SiO2 (D50=0.8 μm, oxygen content about 0.6 wt%) and glucose. Mix the high-purity SiO2 powder and glucose according to the molar ratio of C to SiO2 of 2.4:1 to obtain a mixture.

[0053] (2) Place the mixture obtained in step (1) in a reactor, heat it to 750°C, introduce N2, and react for 2 hours to obtain reactant I.

[0054] (3) Keep the gas atmosphere in the reactor constant, raise the temperature to 1350℃, hold for 5 hours, and obtain reactant II.

[0055] (4) Heat-treat reactant II at 700℃ for 4 hours to remove carbon and remove excess carbon source.

[0056] The Si3N4 powder obtained in this comparative example was found to have a lattice oxygen content of 0.22 wt%, a total oxygen content of 0.80 wt%, and a specific surface area (BET) of 6.2 m². 2 / g.

[0057] The above description does not cover all embodiments. The detailed description of embodiments in this disclosure is not intended to limit the scope of the claimed disclosure, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this disclosure without inventive effort are within the scope of protection of this disclosure.

Claims

1. A method for preparing nitrides with low lattice oxygen content, characterized in that, include: S1, mix oxide raw materials and carbon source to obtain precursor, wherein the oxide raw materials are Al2O3 powder or SiO2 powder; S2, the precursor is placed in a reactor and heated to 700~900°C. A first mixed gas containing N2 and halogen gas is introduced for activation to obtain the activated product. S3, heat to 1300~1600℃, keep the gas atmosphere constant, and carry out carbothermic reduction of the activated product to obtain the reduced product; S4. Keeping the temperature of the reactor constant, a passivating agent is introduced to generate a sealing layer on the surface of the reduction product, resulting in a nitride with low lattice oxygen content.

2. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, In step S2, the halogen gas is selected from Cl2 and / or CCl4, and the volume fraction of the halogen gas in the first mixed gas is 10~20%.

3. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, In step S2, the activation time is 1~3 hours.

4. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, In step S3, the furnace cavity of the reactor is controlled to be in a slightly negative pressure state of -0.02 to -0.04 MPa.

5. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, When the oxide raw material is Al2O3, in step S4, the passivating agent is SiCl4 to generate a Si3N4 sealing layer on the surface of the reduction product.

6. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, When the oxide raw material is SiO2, in step S4, the passivating agent is AlCl3 to generate an AlN sealing layer on the surface of the reduction product.

7. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, In step S3, the carbothermic reduction reaction takes 3-4 hours.

8. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, In step S1, the molar ratio of the carbon source to the oxide raw material is 98% to 102% of their stoichiometric ratio.

9. The method for preparing nitrides with low lattice oxygen content according to claim 1, characterized in that, In step S4, after the passivating agent is introduced for 8-15 minutes, argon quenching is performed.

10. A nitride with low lattice oxygen content, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9.

Images